I am working on a car which has 3/4" molded heater hoses going to the heater core. Both of these hoses are swollen up to 7/8" ID, but do not feel squishy, and the ends at the heater core do not feel damaged, and no evidence of leakage there. There is no access to the heater core fittings to replace the hoses, unless the steering rack is removed (way too much work) or the car is raised on a lift, and accessed from below (unfortunately, I am not a shop and don’t have a lift).
The problem is that the opposite ends of these hoses are bad. One end goes to the cylinder head, and one end goes to the coolant crossover pipe. I already cut off 5½" of the hose going to the cylinder head, and want to cut off the molded 90° going to the crossover pipe. The hose is starting to crack and leak at the nipple on the crossover pipe.
Now I can obviously buy a 3/4" 90° cut-to-fit heater hose, and a length of 3/4" straight heater hose, but I am having difficulty finding a suitable fitting for going from 3/4" to 7/8". Online research indicates that 3/4" hose is equivalent to 19mm and 7/8" hose is equivalent to 22mm, and that 22mm is a hose size used in some boats, but not for automotive use. I could only find one company selling this fitting online, and it would cost about $76 with shipping for two of them, all the way from Taiwan.
Since I am not really interested in paying that much for two aluminum fittings, I’m looking for other ideas. One idea that I have seen floated online for this situation is to use copper pipe of both sizes, solder or braze them together, and then put a bead of solder or brazing alloy around each end to act as a lip. This seems like a lot of effort, though, so I am looking for other ideas. I own a hydra-swage, and have access to scrap refrigeration-grade copper pipe at work, so I could certainly manufacture such adapters if necessary.
Any suggestions on how to join new hoses to these existing hoses as cheaply and easily as possible?